1 /* 2 * arch/arm/include/asm/fncpy.h - helper macros for function body copying 3 * 4 * Copyright (C) 2011 Linaro Limited 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 18 */ 19 20 /* 21 * These macros are intended for use when there is a need to copy a low-level 22 * function body into special memory. 23 * 24 * For example, when reconfiguring the SDRAM controller, the code doing the 25 * reconfiguration may need to run from SRAM. 26 * 27 * NOTE: that the copied function body must be entirely self-contained and 28 * position-independent in order for this to work properly. 29 * 30 * NOTE: in order for embedded literals and data to get referenced correctly, 31 * the alignment of functions must be preserved when copying. To ensure this, 32 * the source and destination addresses for fncpy() must be aligned to a 33 * multiple of 8 bytes: you will be get a BUG() if this condition is not met. 34 * You will typically need a ".align 3" directive in the assembler where the 35 * function to be copied is defined, and ensure that your allocator for the 36 * destination buffer returns 8-byte-aligned pointers. 37 * 38 * Typical usage example: 39 * 40 * extern int f(args); 41 * extern uint32_t size_of_f; 42 * int (*copied_f)(args); 43 * void *sram_buffer; 44 * 45 * copied_f = fncpy(sram_buffer, &f, size_of_f); 46 * 47 * ... later, call the function: ... 48 * 49 * copied_f(args); 50 * 51 * The size of the function to be copied can't be determined from C: 52 * this must be determined by other means, such as adding assmbler directives 53 * in the file where f is defined. 54 */ 55 56 #ifndef __ASM_FNCPY_H 57 #define __ASM_FNCPY_H 58 59 #include <linux/types.h> 60 #include <linux/string.h> 61 62 #include <asm/bug.h> 63 #include <asm/cacheflush.h> 64 65 /* 66 * Minimum alignment requirement for the source and destination addresses 67 * for function copying. 68 */ 69 #define FNCPY_ALIGN 8 70 71 #define fncpy(dest_buf, funcp, size) ({ \ 72 uintptr_t __funcp_address; \ 73 typeof(funcp) __result; \ 74 \ 75 asm("" : "=r" (__funcp_address) : "0" (funcp)); \ 76 \ 77 /* \ 78 * Ensure alignment of source and destination addresses, \ 79 * disregarding the function's Thumb bit: \ 80 */ \ 81 BUG_ON((uintptr_t)(dest_buf) & (FNCPY_ALIGN - 1) || \ 82 (__funcp_address & ~(uintptr_t)1 & (FNCPY_ALIGN - 1))); \ 83 \ 84 memcpy(dest_buf, (void const *)(__funcp_address & ~1), size); \ 85 flush_icache_range((unsigned long)(dest_buf), \ 86 (unsigned long)(dest_buf) + (size)); \ 87 \ 88 asm("" : "=r" (__result) \ 89 : "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1))); \ 90 \ 91 __result; \ 92 }) 93 94 #endif /* !__ASM_FNCPY_H */ 95